Connection between two shaft ends, positioned coaxially one behind the other, of a gas shuttle valve in an internal combustion engine and a valve actuator

ABSTRACT

The present invention relates to a connection between two shaft ends ( 8, 10 ), situated coaxially one behind the other, of a gas exchange valve ( 1 ) of an internal combustion engine and a piston rod ( 2 ) of a valve actuator ( 4 ), where at least one coupling member ( 14 ) at least partially surrounds the shaft ends ( 8, 10 ).  
     The present invention provides for the coupling body ( 14 ) to be radially tensioned with respect to the two shaft ends ( 8, 10 ) by at least one tensioning member ( 34, 36 ) to produce static friction locking between each shaft end ( 8, 10 ) and the coupling member ( 14 ) that transfers the actuating motion of valve actuator ( 4 ) to gas exchange valve ( 1 ) in a slip-free manner. As a result, the fatigue strength of the connection is able to be increased and its assembly and disassembly is simplified.

BACKGROUND INFORMATION

[0001] The present invention starts out from a connection between twoshaft ends, situated coaxially one behind the other, of a gas exchangevalve of an internal combustion engine and of a valve actuator, where atleast one coupling member according to the definition of the species setforth in Patent claim 1 at least partially surrounds the shaft ends.

[0002] Such a connection is known from EP 0 279 265 B1, where thecoupling member includes two half-shells whose radially externalperipheral surfaces are cylindrical and whose radially internalperipheral surfaces are conical in a manner complimentary to the pistonrod ends of the valve actuator, which are tapered conically with respectto one another, and to a shaft of the gas exchange valve. To prevent thetwo half-shells from falling apart, a cylindrical coupling sleeve heldto the half-shells by the axial prestress force of a valve springsupported on the bottom of the screw sleeve is pushed over them, theshaft of the gas exchange valve extending through an opening in thebottom of the screw sleeve. The two shaft ends, which are taperedrelatively to each other, have at the extremity flanges that are widenedin a plate-like manner and grip the coupling member formed by thehalf-shells from behind, so that the two shaft ends are connected to oneanother by the coupling member in a form-locking manner. At theform-locking junction between the conical runout of the shaft ends andthe extreme flanges, the cross section is weakened in each case by adistinct groove, which has a negative effect on the fatigue strength ofthe connection. This represents a significant disadvantage especiallywith regard to the high number of load changes that gas exchange valvesof internal combustion engines are subjected to.

SUMMARY OF THE INVENTION

[0003] Due to the frictionally engaged connection between the couplingmember and the shaft ends, no undercuts are necessary that asgroove-like indentations would weaken the cross section of the shaftends and/or of the coupling member. Consequently, the connection of thepresent invention is distinguished by a high degree of fatigue strength.

[0004] According to a particularly preferred measure, the prestressapplied to the coupling member by the tensioning member is adjustable.For this purpose, the tensioning member includes at least two conicaltensioning sleeves able to be axially screwed against one another andhaving conical surfaces that are able to be wedged against conicaltensioning surfaces formed on the radially external peripheral surfaceof the coupling member, a defined radial prestress being able to begenerated between the coupling member and the shaft ends as function ofthe degree of tightening of the conical tensioning sleeves. This isadvantageous above all with regard to the surface conditions that maydiffer depending on the gas exchange valve or the valve actuator and tothe correspondingly different friction coefficient in that the radialprestress necessary for slip-free static friction locking may beadjusted.

[0005] Viewed in the circumferential direction, the coupling member hasa multi-part design and preferably includes at least two halfpipe-shaped coupling wedges, which complement one another to form asleeve, each coupling wedge having on its outer peripheral surface twotensioning surfaces situated radially one behind the another andexpanding conically with respect to one another, each tensioning surfacebeing assigned to one conical surface of one of the conical tensioningsleeves. Both conical tensioning sleeves are expediently provided with acontact surface for a screw tool.

[0006] According to a further refinement, positioning projections andpositioning recesses that preferably intermesh with play are provided onthe coupling member and on each shaft end for positioning the couplingmember on the shaft ends. This ensures that the coupling member istensioned in a defined position with respect to the shaft ends, and abalanced surface covering results. On the other hand, the looseintermeshing of the positioning projections and recesses reduces fatiguestrength-lowering notch stresses. According to a preferred measure, theradially internal, cylindrical peripheral surface of the coupling wedgeshas annular protuberances that extend in the circumferential direction,each annular protuberance being assigned to an annular groove of a shaftend. The annular protuberances and annular grooves have an essentiallysemicircular cross section, the inner radius of the annular groovesbeing greater than the outer radius of the annular protuberance in orderto prevent direct material contact as much as possible and to keep thenotch stresses caused by the annular grooves as low as possible.

[0007] Finally, the connection between the valve actuator and the gasexchange valve is preferably situated in an accessible region outside ofa valve actuator housing. Therefore, in the event that repairs areneeded, it is very easy to replace a gas exchange valve or a valveactuator, and it is not necessary to dismantle the valve actuator.

[0008] Advantageous further refinements and improvements of theinvention specified in claim 1 are rendered possible by the additionalmeasures specified in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] An exemplary embodiment of the present invention is representedin the drawing and explained in detail in the following description. Thefigures show:

[0010]FIG. 1 shows a lateral view of a cross section of a preferredspecific embodiment of a connection of the invention between a shaft endof a gas exchange valve of an internal combustion engine and a pistonrod of a valve actuator;

[0011]FIG. 2 shows a view of a cross section along line II-II from FIG.1;

[0012]FIG. 3 shows an enlarged view of detail A from FIG. 1.

DETAILED DESCRIPTION

[0013] Only a gas exchange valve 1 of a valve mechanism of an internalcombustion engine is shown in FIG. 1 that is actuated by a piston rod 2of a valve actuator 4 such that it performs upward and downward openingand closing movements. For this purpose, piston rod 2 of valve actuator4 and a shaft 6 of gas exchange valve 1 are situated coaxially onebehind the other, a shaft end 8 of piston rod 2 and a shaft end 10 ofshaft 6 of gas exchange valve 1 being situated opposite one another.Piston rod 2 and shaft 6 of gas exchange valve 1 preferably have thesame diameter. To be able to transfer the pressing motion and/or pullingmotion of piston rod 2 to gas exchange valve 1, a coupling member 14 isprovided that at least partially surrounds shaft end 8 of piston rod 2as well as shaft end 10 of gas exchange valve 1. Viewed in thecircumferential direction, coupling body 14 preferably has a multi-partdesign and includes two half pipe-shaped coupling wedges 16, 18, whichcomplement one another to essentially form a sleeve, as is best seen inthe sectional view in FIG. 2. The radially internal peripheral surfacesof both coupling wedges 16, 18 are cylindrical and have the same radiusas piston rod 2 and shaft 6 of gas exchange valve 1. Viewed in thecircumferential direction, both coupling wedges 16, 18 do not connect toone another without gap, but a narrow opening 20 remains at both joints,so that there is a circumferential compensation for both coupling wedges16, 18 when a radial pressure is exerted on them from the outside.

[0014] As can best be seen in FIG. 1, intermeshing positioningprojections and positioning recesses are provided on coupling member 14and on each shaft end 8, 10 for positioning coupling member 14 on shaftends 8, 10. This ensures that coupling member 14 is situated in adefined position with respect to both shaft ends 8, 10 and that abalanced surface covering results. According to the preferred specificembodiment, each radially internal, cylindrical peripheral surface ofboth coupling wedges 14, 16 has two annular protuberances extending inthe circumferential direction, a top annular protuberance 22 engagingwith a circumferential annular groove 24 formed on shaft end 8 of pistonrod 2, and a bottom annular protuberance 26 engaging with an annulargroove 28 in a shaft end 10 of gas exchange valve 1. Annularprotuberances 22, 26 and annular grooves 24, 28, which are assigned toone another, have an essentially semicircular cross section as can beseen in enlarged view A in FIG. 3 in particular. Annular protuberances22, 26 do not abut against annular grooves 24, 28 of the shaft endssince their inner radius is greater than the outer radius of annularprotuberances 22, 26.

[0015] Both half pipe-shaped coupling wedges 16, 18 have on theirradially external peripheral surface tensioning surfaces 30, 32 disposedone behind the other and expanding conically toward one another in orderto be able to tension coupling wedges 16, 18 radially with respect toboth shaft ends 8, 10. For this purpose, a tensioning member, preferablytwo conical tensioning sleeves 34, 36, which are able to be axiallyscrewed against each other and have conical surfaces 38, 40, is providedthat is able to be wedged against tensioning surfaces 30, 32 of couplingwedge 16, 18, a defined radial prestress being able to be producedbetween coupling wedges 16, 18 and both shaft ends 8, 10 as a functionof the screwing degree of the two conical tensioning sleeves 34, 36.Since the motion of piston rod 2 of valve actuator 4 is to betransferred to gas exchange valve 1 in a slip-free manner, the prestressmust be so great that there is always static friction between couplingwedges 16, 18 and shaft ends 8, 10 under the forces acting duringoperation. Of the two tensioning surfaces 30, 32 of a coupling wedge 16,18, a top tensioning surface 30 is assigned in each case to a conicalsurface 38 of top conical tensioning sleeve 34, and a bottom tensioningsurface 32 is assigned in each case to a conical surface 40 of bottomconical tensioning sleeve 36. Top conical tensioning sleeve 34 is ableto be screwed into bottom conical tensioning sleeve 36 in that radiallyexternal peripheral surface of top conical tensioning sleeve 34 isprovided with an external thread 42, and the radially internalperipheral surface of bottom conical tensioning sleeve 36 is providedwith an internal thread 44 having the same diameter. Both conicaltensioning sleeves 34, 36 are provided at their ends facing away fromone another with a contact surface 48, 50 for a screw tool. Threads 42,44 are consequently outside of the force flux that arises when the valveis actuated and extends from piston rod 2 over the two coupling wedges16, 18 to shaft 6 of gas exchange valve 1 and is only subjected to thestatic prestress for procuring the friction locking between couplingwedges 16, 18 and shaft ends 8, 10. Since annular protuberances 22, 26of both coupling wedges 16, 18 do not rest against annular grooves 24,28 of shaft ends 8, 10, the form locking portion generated by couplingwedges 16, 18 being radially pressed outweighs the form locking portioncaused by the mutually assigned annular protuberance/annular groovepairings in the case of the coupling of piston rod 2 and shaft 6 of gasexchange valve 1. Consequently, the annular protuberance/annular groovepairings are foremost used to fix coupling member 14 to shaft ends 8, 10and can, therefore, have small dimensions. Consequently, their stressconcentration at shaft ends 8, 10 and their influence on the fatiguestrength of the connection is minimal.

[0016] As seen in FIG. 1, the described connection between piston rod 2of valve actuator 4 and shaft 6 of the gas exchange valve is situatedoutside of a valve actuator housing 52 of valve actuator 4 in an easilyaccessible region, so that valve actuator 4 and gas exchange valve 1 areboth easy to assemble and disassemble as individual modules.

[0017] According to a further specific embodiment, coupling member 14 isalso able to be designed as a one-piece sleeve instead of as a two-piecesleeve, a continuous slit extending in the axial direction needing to beprovided in this case in the wall of the sleeve in order to enablecompensating motion of the one-piece sleeve in the circumferentialdirection when radial prestress is applied from the outside by the wedgeeffect of conical tensioning sleeves 34, 36.

What is claimed is:
 1. A connection between two shaft ends (8, 10),situated coaxially one behind the other, of a gas exchange valve (1) ofan internal combustion engine and a piston rod (2) of a valve actuator(4), where at least one coupling member (14) at least partiallysurrounds the shaft ends (8, 10), wherein the coupling body (14) isradially tensioned with respect to the two shaft ends (8, 10) by atleast one tensioning member (34, 36) to produce static friction lockingbetween each shaft end (8, 10) and the coupling member (14) thattransfers the actuating motion of valve actuator (4) to gas exchangevalve (1) in a slip-free manner.
 2. The connection as recited in claim1, wherein the tensioning member includes at least two conicaltensioning sleeves (34, 36), which are able to be axially screwedagainst one another, having conical surfaces (38, 40), which are able tobe wedged against conical tensioning surfaces (30, 32), which are formedon the radially external peripheral surface of coupling member (14),thereby making it possible to generate a radial prestress producing thestatic friction locking between the coupling member (14) and the shaftends (8, 10).
 3. The connection as recited in claim 2, wherein viewed inthe circumferential direction, the coupling member has a multi-partdesign and preferably includes at least two half pipe-shaped couplingwedges (16, 18), which complement one another to form a sleeve, each onehaving on its radially external peripheral surface two tensioningsurfaces (30, 32) situated one behind the other and expanding conicallytoward one another, each tensioning surface (30, 32) being assigned to aconical surface (38, 40) of one of the conical tensioning sleeves (34,36).
 4. The connection as recited in claim 2 or 3, wherein both conicaltensioning sleeves (34, 36) are provided with a contact surface (48, 50)for a screw tool.
 5. The connection as recited in one of the precedingclaims, wherein positioning projections (22, 26) and positioningrecesses (24, 28) preferably intermeshing with play are provided on thecoupling member (14) and each shaft end (8, 10) for positioning thecoupling member (14) with respect to the shaft ends (8, 10).
 6. Theconnection as recited in claims 3 through 5, wherein the coupling wedges(16, 18) have on their radially internal, cylindrical peripheral surfaceat least two annular protuberances (22, 26), which extend in thecircumferential direction, at least one annular protuberance (22, 26)being assigned to one annular groove (24, 28) of a shaft end (8, 10). 7.The connection as recited in claim 6, wherein the annular protuberances(22, 26) and annular grooves (24, 28) have an essentially semicircularcross section, the inner radius of the annular grooves (24, 28) beinggreater than the outer radius of the annular protuberances (22, 26). 8.The connection as recited in one of the preceding claims, wherein it issituated in an accessible region outside of a valve actuator housing(52).